Over 1.1 million breast biopsies are performed each year in the United States alone. Of these, about 80% of the lesions excised during biopsy are found to be benign while about 20% of these lesions are malignant.
In the field of breast cancer, stereotactically guided and percutaneous biopsy procedures have increased in frequency as well as in accuracy as modem imaging techniques allow the physician to locate lesions with ever-increasing precision. However, for any given biopsy procedure, a subsequent examination of the biopsy site is very often desirable. There is an important need to determine the location, most notably the center, as well as the orientation and periphery (margins) of the subcutaneous cavity from which the lesion is removed.
In those cases where the lesion is found to be benign, for example, a follow-up examination of the biopsy site is often performed to ensure the absence of any suspect tissue and the proper healing of the cavity from which the tissue was removed. This is also the case where the lesion is found to be malignant and the physician is confident that all suspect tissue was removed and the tissue in the region of the perimeter or margins of the cavity is “clean”.
In some cases, however, the physician may be concerned that the initial biopsy failed to remove a sufficient amount of the lesion. Such a lesion is colloquially referred to as a “dirty lesion” or “dirty margin” and requires follow-up observation of any suspect tissue growth in the surrounding marginal area of the initial biopsy site. Thus, a re-excision of the original biopsy site must often be performed. In such a case, the perimeter of the cavity must be identified since the cavity may contain cancerous cells. Identification of the cavity perimeter is necessary to avoid the risk of opening the cavity, which could release and spread cancerous cells. Moreover, the site of the re-excised procedure itself requires follow-up examination, providing further impetus for accurate identification of the location of the re-excised site. Therefore, a new marker will be placed after re-excision.
Prior methods of marking biopsy cavities utilize one or more tissue marking clips as the biopsy site marking device. Most commonly, these marker clips have a “horseshoe” configuration. The marker clips attach to the walls of the cavity when the free ends or limbs of the “horseshoe” are pinched together, trapping the tissue. This device has significant drawbacks.
For instance, prior to placing the marker clip at the cavity site, the site must be thoroughly cleaned, typically by vacuum, to remove any residual tissue debris. This minimizes the possibility that the marker clip attaches to any loose tissue as opposed to the cavity wall. Once the cavity is prepared, the clip must be examined to ensure that the limbs of the clip are substantially straight. If the limbs have been prematurely bent together, the clip will be discarded since it will most likely not attach properly to the cavity wall. Actual placement of the clip often requires additional vacuum of the cavity wall to draw the wall into the aperture between the limbs of the marking clip so that a better grip is obtained between the limbs of the clip. Additionally, there is always the possibility that the clip may detach from the cavity wall during or after withdrawal of the tools used to place the clip into the cavity.
Aside from the problems inherent in the placement of the marking clip, there are also limitations associated with how well the marking clip can identify a biopsy cavity. As the marking clip must trap tissue for proper attachment, in cases of endoscopic placement, the clip can only be placed on a wall of the cavity substantially opposite to the opening of the cavity.
Moreover, patient concern limits the number of clips that may be placed in a cavity. As a result, the medical practitioner is forced to identify the outline of a three dimensional cavity by a single point as defined by the marking clip. Obviously, determination of the periphery of a biopsy cavity from one point of the periphery is not possible.
These limitations are compounded as the biopsy cavity fills within a few hours with bodily fluids, which eventually renders the cavity invisible to noninvasive techniques. Another difficulty in viewing the clip stems from the fact that the clip is attached to the side, not the center, of the cavity. This makes determining the spatial orientation and position of the cavity difficult if not impossible during follow-up examination. Additionally, during a stereotactic breast biopsy procedure, the breast is under compression when the marking clip is placed. Upon release of the compressive force, determining the location of the clip can be unpredictable, and the orientation as well as the location of the periphery of the cavity are lost.
The marker clip does not aid in the healing process of the biopsy wound. Complications may arise if the marker strays from its original placement site. As described above, if a re-excision of the site is required, the marker clip may also interfere when excision of a target lesion is sought.
Other devices pertaining to biopsy aids are directed to assisting in the healing and closure of the biopsy wound; thus they do not aid the clinical need or desirability of accurately preserving the location and orientation of the biopsy cavity. See, e.g., U.S. Pat. Nos. 4,347,234, 5,388,588, 5,326,350, 5,394,886, 5,467,780, 5,571,181, and 5,676,146.